Preparation and utility of water-soluble polymers having pendant derivatized amide, ester or ether functionalities as ceramics dispersants and binders

ABSTRACT

Methods for dispersing and binding ceramic materials in aqueous media are disclosed. The methods utilize water-soluble polymers having pendant derivatized amide, ester or ether functionalities for dispersing and binding various classes of ceramic materials.

This application is a divisional of Ser. No. 08/982,590, filed Dec. 4,1997, now U.S. Pat. No. 5,880,237, which is a continuation-in-part ofco-pending application Ser. No. 08/792,610, filed Jan. 31, 1997 entitled"Preparation and Utility of Water-Soluble Polymers having PendantDerivatized Amide, Ester or Ether Functionalities as CeramicsDispersants and Binders now U.S. Pat. No. 5,726,267."

FIELD OF THE INVENTION

Methods for dispersing and binding ceramic materials in aqueous mediaare disclosed. The methods utilize water-soluble polymers having pendantderivatized amide, ester or ether functionalities for dispersing andbinding various classes of ceramic materials.

BACKGROUND OF THE INVENTION

Ceramic materials are commonly prepared by mixing powdered ceramicoxides such as magnesia, alumina, titania and zirconia, in a slurryalong with additives, such as dispersants and binders. The slurry may bespray dried to produce ceramic particles. The particles are pressed intoan aggregate structure, called a "green ceramic," having a desired shapeand subsequently subjected to a severe heat treatment known assintering. The sintering process converts the green ceramic into acohesive "fired ceramic", having a nearly monolithic polycrystallineceramic phase.

The binder serves to hold the ceramic particles of the green ceramic inthe desired shape after pressing. The binder can also providelubrication while the particles are pressed. Preferably, the bindercombusts or vaporizes completely during the sintering process leaving notrace of the binder in the fired ceramic. In performing these functions,binders significantly affect the properties of the fired ceramics whichare ultimately produced.

In commercial practice, poly(vinyl alcohols) are widely used as ceramicbinders. Additionally, poly(ethylene oxide) and ethylene-vinyl acetatecopolymers reportedly have been used as binders for particulatematerial, such as granular silica gel.

For example, polymeric binders containing substantially hydrolyzedcopolymers made from monomers having ester or amide functional groups,poly(vinylformamide) or a copolymer of vinyl alcohol and vinyl amine aredisclosed in U.S. Pat. Nos. 5,358,911; 5,487,855 and 5,525,665.

Furthermore, polymeric treatments have been disclosed in U.S. Pat. Nos.4,680,339; 4,731,419; 4,885,345 and 5,084,520. Utility for thetreatments has been disclosed to be as dispersants in water treatment,scale inhibitors in industrial and natural waters, flocculants,coagulants and thickeners; but ceramics applications of binding anddispersancy have not been disclosed.

Although commercially available binders are satisfactory for manyapplications, a need exists for improved binders which provide stillgreater strength and/or increased density in green ceramic materials.Greater green strength reduces breakage during handling of the greenceramics and, generally, is associated with higher quality firedceramics. Preferably, the improved binders would be cheaper and moreversatile than previously known binders.

Spray drying is an evaporative process in which liquid is removed from aslurry containing a liquid and a substantially non-volatile solid. Theliquid is vaporized by direct contact with a drying medium, usually air,in an extremely short retention time, on the order of about 3 to about30 seconds. The primary controlling factors in a spray drying processare particle size, particle size distribution, particle shape, slurrydensity, slurry viscosity, temperature, residence time, and productmoisture.

The viscosity of the slurry must be suitable for handling andspray-drying. Although spray-drying equipment conditions may be adjustedto handle a variety of viscosities, larger particles will usually resultfrom higher viscosity slurries.

Those of ordinary skill in the art are familiar with the spray-dryingprocess used in the production of ceramic materials, and will be able tooptimize the control factors of spray-drying to best advantage.Alternatively, the spray drying process may be replaced by other wellknown drying methods, such as granulation, tape casting and slipcasting.

Spray drying of the slurry produces substantially dry, free-flowingpowder particles which contain the ceramic, the binder and the optionalmaterials described above. The dry particles are granules which aregenerally spheroidal in shape and have an effective diameter of about 50to about 300 micrometers. Typically, about 0.5 percent to about 8percent of the binder, based on the dry weight of the ceramic powder, ispresent in the dry particles.

In granulation, a mixture of dry powder or powders is mixed or rolled,commonly in a barrel shaped apparatus. Water and/or a binder solution issprayed into the mixing powder causing aggregation of the smallparticles into larger granules. The size of the granules is controlledby the amount of material sprayed into the powders and the speed withwhich it is sprayed. Granulated powders may be screened to a desiredsize and pressed to shape in a pressing operation prior to sintering.Alternatively, the granules themselves may be the desired product andmay be sintered directly.

Tape casting is commonly used to produce thin substrates for thecomputer industry. In the process, a thick ceramic slurry containingceramic powder, dispersant and binders is prepared. This slurry is castonto a smooth surface such as a Mylar or plastic sheet and the thicknessis controlled by passing the sheet under a blade which smoothes theslurry surface and scrapes off excess material. The slurry tape is driedto a plastic state and cut and shaped to specification. The amount ofbinders present in tape casting is very high, typically on the order of15 to 20 wt. % of the ceramic powder mass.

In fluidized bed spray drying, small "seed" particles are placed in acolumn and hot air is blown into the seed powder from below suspendingthe particles in the column. A ceramic slurry is sprayed onto the seedparticles from above, causing them to grow. When the particles reach alarge enough size, they are siphoned out of the dryer while more seedparticles are introduced. This process can produce powder for furtherforming processes, or the powder itself may represent the desiredproduct, in which case it would be sintered to produce the finalceramic.

The dry particles are compacted to produce an aggregate, green ceramicstructure. Preferably, the particles are compacted by pressing in dieshaving an internal volume which approximates the shape desired for thefinal fired ceramic product. Alternatively, the particles are compactedby roll compacting or other well-known compacting methods. The spraydried blend of powder, binder, and optional surfactants and lubricantsis relatively free flowing so that it can enter and closely conform tothe shape of the pressing dies.

Inside the dies, the dry particles are subjected to a pressure which istypically in the range of about 5000 to about 50,000 psi. Pressing theparticles produces an aggregate structure, called a green ceramic, whichretains its shape after removal from the die.

One forming technique used for spray dried or granulated material isroll compaction, also referred to as roll pressing. This technique takesa dry powder and crushes it between two rollers in a continuous process.This process produces sheets of ceramic of various widths andthicknesses. These sheets can be cut to shape and sintered to producethe final ceramic body. The process is commonly used to produce ceramicsubstrates for the electronics industry.

Dry pressing involves filling a shaped die with spray dried orgranulated powder and pressing it at high pressures. The pressing occursthrough movable pistons at the top and/or bottom of the die cavity. Theprocess can be used to produce fairly complex geometries in a singleforming step. The ceramic body that results is ejected from the die andsintered to produce a final ceramic product.

Isostatic pressing is similar to dry pressing in that a ceramic powderis pressed in a die cavity. In isostatic pressing, however, all or partof the die wall consists of a flexible material. After filling the diecavity with powder, the die is submerged in a liquid pressure chamberand pressure is applied to squeeze the die and compact the powder.Unlike dry pressing, no movable parts are involved. Isostatic pressingis commonly used on large or very long parts to minimize cracking orlamination of the final ceramic green body.

Extrusion involves the pushing of a concentrated, plastic, slurrythrough an orifice. The orifice is of the size and shape of the desiredceramic body. This process is commonly used to produce ceramic tubes orsimilarly shaped pieces. The slurry used is prepared from dry powderswhich are mixed with water, organic binders and lubricants, and acoagulant. This slurry is usually predried in a filter press or similarapparatus to remove excess water and thicken the slurry to a plasticmaterial. The material is then extruded through a press which is eitherpiston or screw driven. The extruded material is cut to length, dried,and sintered.

Jiggering is commonly used in the whiteware industry to shape anextruded or filter pressed ceramic slurry. Typically, a portion of theplastic slurry is placed on a rotating wheel and shaped by rollersand/or knife blades to a desired geometry. This body is then dried andsintered.

Another ceramic forming method, that is used for parts of complex shape,is slip casting. In slip casting, a concentrated ceramic slurry (slip)is poured into a mold with an internal shape of the desired ceramicbody. The slurry used must be highly concentrated to prevent settling ofparticles and/or excessive shrinkage during drying. At the same time,the slip must be fluid enough to completely fill the mold and allowescape of air bubbles. The presence of a polymeric binder adds strengthto the cast body preventing breakage during mold removal and handling ofthe body prior to sintering.

Heating the aggregate structure drives off volatile materials such aswater, and bums off organic materials, such as binders or surfactants.When a sufficiently high temperature is reached, the particles of theaggregate structure begin to fuse, but do not fuse completely, andbecome fastened to one another to reproduce a relatively strong firedceramic material having essentially the desired shape.

The slurry is, for example, spray dried to produce substantially dryparticles. The particles are preferably pressed to produce an aggregate,green ceramic structure and heated to produce a fired ceramic material.Alternatively, the particles can be formed into an aggregate, greenceramic structure by roll compaction or other well-known methods.

Although commercially available binders are satisfactory for manyapplications, a need exists for improved binders which provide stillgreater strength and/or high density in green ceramic materials. Greatergreen strength reduces breakage during handling of the green ceramicsand, generally, is associated with higher quality fired ceramics.Preferably, the improved binders would be cheaper and more versatilethan previously known binders.

The present invention also relates to a method for dispersing ceramicmaterials. In particular, the present invention relates to a method fordispersing one or more ceramic materials in an aqueous medium by using apolymeric dispersant formed from acid-containing monomers and hydroxyfunctional monomers.

Ceramic materials are often used to prepare lightweight, strong,thermally and chemically resistant products. Because of difficultiesassociated with the handling of solid ceramic materials, it is desirablefor the ceramic materials to be in the form of an aqueous dispersion.Aqueous dispersions of ceramic materials are, however, often unstable,exhibiting sediment formation upon standing. Upon standing, thedispersion agglomerates and becomes non-homogeneous, and createsdifficulty in handling. These agglomerates may also damage pipes, pumps,and other dispersion handling mechanical equipment. The use ofdispersants overcomes these difficulties, and also improves strength anddensity of formed ceramic parts, particularly those made by dry press,slip casting, and tape casting processes.

Polymers are known for use as dispersants for ceramic materials. Typicalpolymeric dispersants for ceramic materials include polymers formed fromacid-containing monomers such as, for example, poly(acrylic acid) andpoly(methacrylic acid). For example, anionic polymers produced byhydrolyzing a terpolymer of maleic anhydride, N-vinylpyrrolidinone and avinyl compound selected from the group consisting of acrylic acid,acrylamide, methyl methacrylate and butyl vinyl ether is disclosed inU.S. Pat. No. 5,266,243. Additionally, polymeric dispersants consistingof from 5 to 95 percent by weight of one or more hydroxy functionalmonomers and from 95% to 5% by weight of one or more acid-containingmonomers are disclosed in U.S. Pat. Nos. 5,567,353 and 5,532,307. Thehydroxy functional monomer is selected from the group consisting ofhydroxypropyl acrylate, hydroxypropyl methacrylate, hydroxyethylacrylate, hydroxyethyl methacrylate, allyl alcohol, allyloxyethanol,allyl propoxylate, vinyl acetate, 1-butene-3,4-diol and3-allyloxy-1,2-propane diol.

Furthermore, imidized acrylic polymers have been disclosed for theincrease of flowability in cement compositions in U.S. Pat. No.5,393,343.

While such polymers perform adequately in dispersing some ceramicmaterials, certain ceramic materials are more difficult to disperse, andconventional polymeric dispersants are not adequate. Ceramic materialswhich present particular difficulty in forming dispersions includenitrides such as, for example, boron nitride. U.S. Pat. No. 5,209,885describes dispersing silicon nitride for extrusion by the use of a graftcopolymer comprising a polyoxyalkylene backbone with polyacrylate sidechains.

The present invention seeks to provide a method for dispersing ceramicmaterial, including several ceramic materials known to be difficult todisperse.

SUMMARY OF THE INVENTION

Methods for dispersing and binding ceramic materials in aqueous mediaare disclosed. The methods utilize water-soluble polymers having pendantderivatized amide, ester or ether functionalities for dispersing andbinding various classes of ceramic materials.

DESCRIPTION OF THE INVENTION

Each of the five classes of polymers described herein may also haveutility for mining applications such as dust control and red mudflocculation; for cooling water treatment such as scale and corrosioninhibition, such as for calcium carbonate and calcium phosphonate scaleinhibition; for ceramics applications such as green machining and coreforming process of gypsum wall board; for the preparation of gypsumslurries, for reverse osmosis system treatment such as desalinationscale inhibition, for oilfield applications such as reverse emulsionbreakers and barium sulfate and calcium carbonate scale inhibition; fortreatment of pulp and paper systems such as scale control, sizingagents, dry strength additives and release agents and as a treatment forsolids/liquids separation. Such structures can be used in manyapplications such as dispersants in water treatment, scale inhibitors innatural and industrial waters, flocculants, coagulants, and thickenersamong others.

The present invention relates to polymeric binders for preparing ceramicmaterials. The method can be used to produce fired ceramic materialsfrom ceramic powders. Suitable powders include but are not limited to:aluminum oxide, silicon nitride, aluminum nitride, silicon carbide,silicon oxide, magnesium oxide, lead oxide, zirconium oxide, titaniumoxide and neodymium oxide. Aluminum oxide is presently preferred. Thepowder can have a weight-averaged median particle size in the range of afew nanometers to about 1/2 millimeter. Powders having a median size inthe range of about 0.5 to about 10 micrometers are preferred.

In one aspect, the ceramic powder is mixed with an aqueous solutioncontaining a polymer to produce a slurry. Preferably, the solution isprepared using deionized water. The slurry may also contain lubricants,plasticizers and surfactants, such as dispersants and anti-foamingagents.

It is also recognized that the properties of a ceramic such as, but notlimited to, green density, surface quality or milling characteristics,may be varied as desired by adjusting the ratio of the differentmonomers in a copolymer, the degree of hydrolysis of a copolymer and themolecular weight of the polymer used in the binder composition.

Several factors may affect the preferred quantity of the polymericdispersant to be used in forming a dispersion of a ceramic material.Because of the range of ceramic materials that might be used forparticular applications, and because different applications may requiredifferent solids levels, the amount of dispersant may range from 0.01percent to 3 percent by weight based on powder mass. For example, themorphology of the ceramic material may affect the optimum level ofdispersant. Generally, the more spherical the particles, the lessdispersant is required. The surface area of the ceramic material mayalso affect the optimum quantity of dispersant. The higher the surfacearea of a ceramic material, generally the more dispersant is required.

The ionic strength (or water hardness) of the dispersion may also affectthe optimum level of dispersant. Dispersions having higher ionicstrength generally require more dispersant. The ionic strength of thedispersion can be controlled, for example, by using distilled,deionized, partially distilled or partially deionized water, bycontrolling the level of contaminants introduced into the dispersion bythe various components of the dispersion or by adding one or moreconventional chelating agents to the dispersion. Preferably, the waterhardness of the dispersion which is attributable to multivalent cationsis below about 600 parts per million ("ppm") expressed as Ca²⁺, mostpreferably below about 500 ppm. Generally, the higher the pH of thedispersion, the lower the quantity of dispersant required. For purposesof the present invention, it is preferred that the pH not be below 6.The polymeric dispersant of the present invention works particularlywell at a pH of about 8 to 11.

Ceramic materials useful in forming a dispersion according to the methodof the present invention include oxide, nitride, and carbide ceramics;in particular: alumina, aluminum nitride, aluminum titanate, leadtitanate, boron nitride, silicon, silicon carbide, sialon, zirconiumnitride, zirconium carbide, zirconium boride, boron carbide, tungstencarbide, tungsten boride, tin oxide, ruthenium oxide, yttrium oxide,magnesium oxide, calcium oxide, chromic oxide, ferrites, and mixturesthereof among others.

As used herein, "ceramic materials" include ferrites. The ferrites areferrimagnetic oxides. The classes of ferrites include spinel ferrites,which are oxides having the general formula MO.Fe₂ O₃, where "M"represents a divalent metal ion or a mixture of ions. Particularexamples of spinel ferrites are Fe₃ O₄ and NiFe₂ O₄. Another class offerrites is the orthoferrites, with the general formulas MFeO₃, MCoO₃,or MMnO₃, where M represents La, Ca, Sr, Ba Y, or a rare earth ion.Another class of ferrites is the hexagonal ferrites, with the generalformula AB₁₂ O₁₉, where A is a divalent metal and B is a trivalentmetal. Examples of hexagonal ferrites include PbFe₁₂ O₁₉.

The term clays as used herein denotes materials utilized in whitewaremanufacture. Examples are kaolin and ball clay among others.

The polymers described herein for the practice of this invention mayrange in molecular weight from about 1,000 to about 1,000,000.Preferably, the molecular weight will be from about 5,000 to about100,000. For the polymers defined herein, the mer units defined byformulas I-IV will range from 5 to 75% of the total number of mer unitsin the polymer. Preferably, the mer units defined as formulas I-IV willbe at least 30% of the total number of mer units in the polymer.

The polymer classes described herein contain amide, ester and ether merunits which are functionalized with pendant groups. These pendant groupsconfer favorable properties to the polymer for use as a binder forceramic materials. The polymers may be produced by polymerization usingspecific monomers, such as might be produced by the copolymerization ofacrylic acid with a poly(ethylene glycol) methacrylate comonomer. Thepolymer so produced would contain a hydrophilic backbone with pendantgroups comprised of poly(ethylene glycol). Alternatively, pendant groupscould be introduced into the polymer after polymerization. For example,polyacrylic acid could be amidated with an ethoxylated/propoxylatedamine, such as those available from Texaco under the trade nameJeffamine series, to produce a polymer with a hydrophilic backbone andethyleneoxy/propyleneoxy pendant groups. During the amidation process,cyclic imide structures might form between two adjacent carboxylate orcarboxamide units on the polymer backbone. These imide structures arenot expected to have an adverse effect on the performance of thepolymers as a ceramic processing aid.

The invention is a binder for ceramic materials that comprises a watersoluble polymer having:

A) a mer unit of the formula ##STR1## wherein R¹ is selected from thegroup consisting of hydrogen, and C₁ -C₃ alkyl; p and q are integersfrom 1-10; R² and R³ are selected from the group consisting of hydrogenand C₁ -C₃ alkyl; Het¹ and Het² selected from the group consisting of Oand NH with the proviso that Het¹ and Het² are not both oxygen; R⁴ isselected from the group consisting of hydrogen, phosphate, sulfate andC₁ -C₂₀ alkyl; R⁵ and R⁶ are selected from the group consisting ofhydrogen, carboxylate, C₁ -C₃ alkyl, and a cycloalkyl group of 1 to 6carbon atoms formed by the linkage of R⁵ and R⁶ as a ring; and

B) a mer unit selected from the group consisting of acrylic acid,methacrylic acid, acrylamide, maleic anhydride, itaconic acid, vinylsulfonic acid, styrene sulfonate, N-tertbutylacrylamide,butoxymethylacrylamide, N,N-dimethylacrylamide, sodium acrylamidomethylpropane sulfonic acid, vinyl alcohol, vinyl acetate, N-vinylpyrrolidone, maleic acid, and combinations thereof.

As used herein, the monomers described above may be in either their saltor acid forms.

The invention is also an unfired, ceramic precursor material comprisinga mixture of.

A. a ceramic powder selected from the group consisting of aluminumoxide, silicon nitride, aluminum nitride, silicon carbide, siliconoxide, magnesium oxide, lead oxide, zirconium oxide, titanium oxide,steatite, barium titanate, lead zirconate titanate, clays, ferrite,yttrium oxide, zinc oxide, tungsten carbide, sialon, neodymium oxide andcombinations thereof and

B. a water soluble polymer having:

i) a mer unit of the formula ##STR2## wherein R¹ is selected from thegroup consisting of hydrogen, and C₁ -C₃ alkyl; p and q are integersfrom 1-10; R² and R³ are selected from the group consisting of hydrogenand C₁ -C₃ alkyl; Het¹ and Het² selected from the group consisting of Oand NH with the proviso that Het¹ and Het² are not both oxygen; R⁴ isselected from the group consisting of hydrogen, phosphate, sulfate andC₁ -C₂₀ alkyl; R⁵ and R⁶ are selected from the group consisting ofhydrogen, carboxylate, C₁ -C₃ alkyl, and a cycloalkyl group of 1 to 6carbon atoms formed by the linkage of R⁵ and R⁶ as a ring; and

ii) a mer unit selected from the group consisting of acrylic acid,methacrylic acid, acrylamide, maleic anhydride, itaconic acid, vinylsulfonic acid, styrene sulfonate, N-tertbutylacrylamide,butoxymethylacrylamide, N,N-dimethylacrylamide, sodium acrylamidomethylpropane sulfonic acid, vinyl alcohol, vinyl acetate, N-vinylpyrrolidone, maleic acid, and combinations thereof.

The invention is also a method for preparing a ceramic material, whichcomprises the steps of:

A) mixing a ceramic powder with an aqueous solution containing awater-soluble polymer to produce a slurry, said water-soluble polymerhaving:

i) a mer unit of the formula ##STR3## wherein R¹ is selected from thegroup consisting of hydrogen, and C₁ -C₃ alkyl; p and q are integersfrom 1-10; R² and R³ are selected from the group consisting of hydrogenand C₁ -C₃ alkyl; Het¹ and Het² selected from the group consisting of Oand NH with the proviso that Het¹ and Het² are not both oxygen; R⁴ isselected from the group consisting of hydrogen, phosphate, sulfate andC₁ -C₂₀ alkyl; R⁵ and R⁶ are selected from the group consisting ofhydrogen, carboxylate, C₁ -C₃ alkyl, and a cycloalkyl group of 1 to 6carbon atoms formed by the linkage of R⁵ and R⁶ as a ring; and

ii) a mer unit selected from the group consisting of acrylic acid,methacrylic acid, acrylamide, maleic anhydride, itaconic acid, vinylsulfonic acid, styrene sulfonate, N-tertbutylacrylamide,butoxymethylacrylamide, N,N-dimethylacrylamide, sodium acrylamidomethylpropane sulfonic acid, vinyl alcohol, vinyl acetate, N-vinylpyrrolidone, maleic acid, and combinations thereof;

B) drying the slurry by a process selected from the group consisting offluidized bed spray drying, and spray drying to produce particles whichinclude said copolymer;

C) compacting the particles by a process selected from the groupconsisting of dry pressing, roll compaction and isostatic pressing toproduce an aggregate structure; and

D) heating the aggregate structure to produce a fired ceramic material.

Moreover, for the practice of this invention, the particles may beproduced by granulation and the step of compacting the particles toproduce an aggregate structure may be selected from the group consistingof dry pressing and isostatic pressing.

Alternatively, other methods of making ceramics which are suitable forthe purposes of this invention include extrusion, jiggering, tapecasting and slip casting.

The invention is a binder for ceramic materials that comprises a watersoluble polymer having:

A) a mer unit of the formula ##STR4## wherein p is an integer from 1-10;R² and R³ are selected from the group consisting of hydrogen and C₁ -C₃alkyl; R⁴ is selected from the group consisting of hydrogen, phosphate,sulfate and C₁ -C₂₀ alkyl; R⁵ and R⁶ are selected from the groupconsisting of hydrogen, carboxylate, C₁ -C₃ alkyl, and a cycloalkylgroup of 1 to 6 carbon atoms formed by the linkage of R⁵ and R⁶ as aring, with the proviso that when p=1, R², R³, R⁴, R⁵ and R⁶ are not allhydrogens, and with the proviso that when p=1, R⁵ is not methyl; and

B) a water-soluble mer unit selected from the group consisting ofacrylic acid, methacrylic acid, acrylamide, maleic anhydride, itaconicacid, vinyl sulfonic acid, styrene sulfonate, N-tertbutylacrylamide,butoxymethylacrylamide, N,N-dimethylacrylamide, sodium acrylamidomethylpropane sulfonic acid, vinyl alcohol, N-vinyl pyrrolidone, maleic acid,and combinations thereof.

As used herein, the monomers described above may be in either their saltor acid forms.

The invention is also an unfired, ceramic precursor material comprisinga mixture of:

A. a ceramic powder selected from the group consisting of aluminumoxide, silicon nitride, aluminum nitride, silicon carbide, siliconoxide, magnesium oxide, lead oxide, zirconium oxide, titanium oxide,steatite, barium titanate, lead zirconate titanate, clays, ferrite,yttrium oxide, zinc oxide, tungsten carbide, sialon, neodymium oxide andcombinations thereof and

B. a water soluble polymer having:

i) a mer unit of the formula ##STR5## wherein p is an integer from 1-10;R² and R³ are selected from the group consisting of hydrogen and C₁ -C₃alkyl; R⁴ is selected from the group consisting of hydrogen, phosphate,sulfate and C₁ -C₂₀ alkyl; R⁵ and R⁶ are selected from the groupconsisting of hydrogen, carboxylate, C₁ -C₃ alkyl, and a cycloalkylgroup of 1 to 6 carbon atoms formed by the linkage of R⁵ and R6 as aring, with the proviso that when p=1, R², R³, R⁴, R⁵ and R⁶ are not allhydrogens, and with the proviso that when p=1, R⁵ is not methyl; and

ii) a water-soluble mer unit selected from the group consisting ofacrylic acid, methacrylic acid, acrylamide, maleic anhydride, itaconicacid, vinyl sulfonic acid, styrene sulfonate, N-tertbutylacrylamide,butoxymethylacrylamide, N,N-dimethylacrylamide, sodium acrylamidomethylpropane sulfonic acid, vinyl alcohol, N-vinyl pyrrolidone, maleic acid,and combinations thereof.

The invention is also a method for preparing a ceramic material, whichcomprises the steps of:

A) mixing a ceramic powder with an aqueous solution containing awater-soluble polymer to produce a slurry, said water-soluble polymerhaving:

i) a mer unit of the formula ##STR6## wherein p is an integer from 1-10;R² and R³ are selected from the group consisting of hydrogen and C₁ -C₃alkyl; R⁴ is selected from the group consisting of hydrogen, phosphate,sulfate and C₁ -C₂₀ alkyl; R⁵ and R⁶ are selected from the groupconsisting of hydrogen, carboxylate, C₁ -C₃ alkyl, and a cycloalkylgroup of 1 to 6 carbon atoms formed by the linkage of R⁵ and R⁶ as aring, with the proviso that when p=1, R², R³, R⁴, R⁵ and R⁶ are not allhydrogens, and with the proviso that when p=1, R⁵ is not methyl; and

ii) a water-soluble mer unit selected from the group consisting ofacrylic acid, methacrylic acid, acrylamide, maleic anhydride, itaconicacid, vinyl sulfonic acid, styrene sulfonate, N-tertbutylacrylamide,butoxymethylacrylamide, N,N-dimethylacrylamide, sodium acrylamidomethylpropane sulfonic acid, vinyl alcohol, N-vinyl pyrrolidone, maleic acid,and combinations thereof;

B) drying the slurry by a process selected from the group consisting offluidized bed spray drying, and spray drying to produce particles whichinclude said copolymer;

C) compacting the particles by a process selected from the groupconsisting of dry pressing, roll compaction and isostatic pressing toproduce an aggregate structure; and

D) heating the aggregate structure to produce a fired ceramic material.

Moreover, for the practice of this method, the particles may be producedby granulation and the step of compacting the particles to produce anaggregate structure may be selected from the group consisting of drypressing and isostatic pressing.

Alternatively, other methods of making ceramics which are suitable forthe purposes of this invention include extrusion, jiggering, tapecasting and slip casting.

The invention is also a method for dispersing one or more ceramicmaterials in an aqueous medium, comprising utilizing an effectivedispersing amount of a polymeric dispersant comprising a water solublepolymer having:

A) a mer unit of the formula ##STR7## wherein p is an integer from 1-10;R² and R³ are selected from the group consisting of hydrogen and C₁ -C₃alkyl; R⁴ is selected from the group consisting of hydrogen, phosphate,sulfate and C₁ -C₂₀ alkyl; R⁵ and R⁶ are selected from the groupconsisting of hydrogen, carboxylate, C₁ -C₃ alkyl, and a cycloalkylgroup of 1 to 6 carbon atoms formed by the linkage of R⁵ and R⁶ as aring, with the proviso that when p=1, R², R³, R⁴, R⁵ and R⁶ are not allhydrogens, and with the proviso that when p=1, R⁵ is not methyl; and

B) a water-soluble mer unit selected from the group consisting ofacrylic acid, methacrylic acid, acrylamide, maleic anhydride, itaconicacid, vinyl sulfonic acid, styrene sulfonate, N-tertbutylacrylamide,butoxymethylacrylamide, N,N-dimethylacrylamide, sodium acrylamidomethylpropane sulfonic acid, vinyl alcohol, N-vinyl pyrrolidone, maleic acid,and combinations thereof.

Moreover the one or more ceramic materials may be selected from thegroup consisting of alumina, aluminum nitride, aluminum titanate, leadtitanate, boron nitride, silicon, silicon carbide, sialon, zirconiumnitride, zirconium carbide, zirconium boride, boron carbide, tungstencarbide, tungsten boride, tin oxide, ruthenium oxide, yttrium oxide,magnesium oxide, calcium oxide, and ferrites.

Furthermore, the invention is also an aqueous dispersion of ceramicmaterial prepared according to the method above.

The invention is also a binder for ceramic materials that comprises awater soluble polymer having:

A) a mer unit of the formula ##STR8## wherein p is an integer from 1-10;R² and R³ are selected from the group consisting of hydrogen and C₁ -C₃alkyl; R⁴ is selected from the group consisting of hydrogen, phosphate,sulfate and C₁ -C₂₀ alkyl R⁵ and R⁶ are selected from the groupconsisting of hydrogen, carboxylate, C₁ -C₃ alkyl, and a cycloalkylgroup of 1 to 6 carbon atoms formed by the linkage of R⁵ and R⁶ as aring, with the proviso that when p=1, R², R³, R⁴, R⁵ and R⁶ are not allhydrogens and with the proviso that when p=1, R² is not methyl and withthe proviso that when p=1, R³ is not methyl; and

B) a water-soluble mer unit selected from the group consisting ofacrylic acid, methacrylic acid, acrylamide, maleic anhydride, itaconicacid, vinyl sulfonic acid, styrene sulfonate, N-tertbutylacrylamide,butoxymethylacrylamide, N,N-dimethylacrylamide, sodium acrylamidomethylpropane sulfonic acid, vinyl alcohol, N-vinyl pyrrolidone, maleic acid,and combinations thereof.

As used herein, the monomers described above may be in either their saltor acid forms.

The invention is also an unfired, ceramic precursor material comprisinga mixture of:

A. a ceramic powder selected from the group consisting of aluminumoxide, silicon nitride, aluminum nitride, silicon carbide, siliconoxide, magnesium oxide, lead oxide, zirconium oxide, titanium oxide,steatite, barium titanate, lead zirconate titanate, clays, ferrite,yttrium oxide, zinc oxide, tungsten carbide, sialon, neodymium oxide andcombinations thereof and

B. a water soluble polymer having:

i) a mer unit of the formula ##STR9## wherein p is an integer from 1-10;R² and R³ are selected from the group consisting of hydrogen and C₁ -C₃alkyl; R⁴ is selected from the group consisting of hydrogen, phosphate,sulfate and C₁ -C₂₀ alkyl; R⁵ and R⁶ are selected from the groupconsisting of hydrogen, carboxylate, C₁ -C₃ alkyl, and a cycloalkylgroup of 1 to 6 carbon atoms formed by the linkage of R⁵ and R⁶ as aring, with the proviso that when p=1, R², R³, R⁴, R⁵ and R⁶ are not allhydrogens and with the proviso that when p=1, R² is not methyl and withthe proviso that when p=1, R³ is not methyl; and

ii) a water-soluble mer unit selected from the group consisting ofacrylic acid, methacrylic acid, acrylamide, maleic anhydride, itaconicacid, vinyl sulfonic acid, styrene sulfonate, N-tertbutylacrylamide,butoxymethylacrylamide, N,N-dimethylacrylamide, sodium acrylamidomethylpropane sulfonic acid, vinyl alcohol, N-vinyl pyrrolidone, maleic acid,and combinations thereof.

The invention is also a method for preparing a ceramic material, whichcomprises the steps of:

A) mixing a ceramic powder with an aqueous solution containing awater-soluble polymer to produce a slurry, said water-soluble polymerhaving:

i) a mer unit of the formula ##STR10## wherein p is an integer from1-10; R² and R³ are selected from the group consisting of hydrogen andC₁ -C₃ alkyl; R⁴ is selected from the group consisting of hydrogen,phosphate, sulfate and C₁ -C₂₀ alkyl; R⁵ and R⁶ are selected from thegroup consisting of hydrogen, carboxylate, C₁ -C₃ alkyl, and acycloalkyl group of 1 to 6 carbon atoms formed by the linkage of R₅ andR₆ as a ring, with the proviso that when p=1, R², R³, R⁴, R⁵ and R⁶ arenot all hydrogens and with the proviso that when p=1, R² is not methyland with the proviso that when p=1, R³ is not methyl; and

ii) a water-soluble mer unit selected from the group consisting ofacrylic acid, methacrylic acid, acrylamide, maleic anhydride, itaconicacid, vinyl sulfonic acid, styrene sulfonate, N-tertbutylacrylamide,butoxymethylacrylamide, N,N-dimethylacrylamide, sodium acrylamidomethylpropane sulfonic acid, vinyl alcohol, N-vinyl pyrrolidone, maleic acid,and combinations thereof;

B) drying the slurry by a process selected from the group consisting offluidized bed spray drying, and spray drying to produce particles whichinclude said copolymer;

C) compacting the particles by a process selected from the groupconsisting of dry pressing, roll compaction and isostatic pressing toproduce an aggregate structure; and

D) heating the aggregate structure to produce a fired ceramic material.

Moreover, for the practice of this invention, the particles may beproduced by granulation and the step of compacting the particles toproduce an aggregate structure may be selected from the group consistingof dry pressing and isostatic pressing.

Alternatively, other methods of making ceramics which are suitable forthe purposes of this invention include extrusion, jiggering, tapecasting and slip casting.

The invention is also a method for dispersing one or more ceramicmaterials in an aqueous medium, comprising utilizing an effectivedispersing amount of a polymeric dispersant comprising a water solublepolymer having:

A) a mer unit of the formula ##STR11## wherein p is an integer from1-10; R² and R³ are selected from the group consisting of hydrogen andC₁ -C₃ alkyl; R⁴ is selected from the group consisting of hydrogen,phosphate, sulfate and C₁ -C₂₀ alkyl; R⁵ and R⁶ are selected from thegroup consisting of hydrogen, carboxylate, C₁ -C₃ alkyl, and acycloalkyl group of 1 to 6 carbon atoms formed by the linkage of R⁵ andR⁶ as a ring, with the proviso that when p=1, R², R³, R⁴, R⁵ and R⁶ arenot all hydrogens and with the proviso that when p=1, R² is not methyland with the proviso that when p=1, R³ is not methyl; and

B) a water-soluble mer unit selected from the group consisting ofacrylic acid, methacrylic acid, acrylamide, maleic anhydride, itaconicacid, vinyl sulfonic acid, styrene sulfonate, N-tertbutylacrylamide,butoxymethylacrylamide, N,N-dimethylacrylamide, sodium acrylamidomethylpropane sulfonic acid, vinyl alcohol, N-vinyl pyrrolidone, maleic acid,and combinations thereof.

Furthermore, the one or more ceramic materials may be selected from thegroup consisting of alumina, aluminum nitride, aluminum titanate, leadtitanate, boron nitride, silicon, silicon carbide, sialon, zirconiumnitride, zirconium carbide, zirconium boride, boron carbide, tungstencarbide, tungsten boride, tin oxide, ruthenium oxide, yttrium oxide,magnesium oxide, calcium oxide, and ferrites.

The invention is also an aqueous dispersion of ceramic material preparedaccording to the method described above.

The invention is also a binder for ceramic materials that comprises awater-soluble polymer having:

A) a mer unit of the formula ##STR12## wherein R¹ is selected from thegroup consisting of hydrogen, and C₁ -C₃ alkyl; p is an integer from1-10; R⁴ is selected from the group consisting of hydrogen, phosphate,sulfate and C₁ -C₂₀ alkyl; R⁵ and R⁶ are selected from the groupconsisting of hydrogen, carboxylate, C₁ -C₃ alkyl, and a cycloalkylgroup of 1 to 6 carbon atoms formed by the linkage of R⁵ and R⁶ as aring; and

B) a mer unit selected from the group consisting of acrylic acid,methacrylic acid, acrylamide, maleic anhydride, itaconic acid, vinylsulfonic acid, styrene sulfonate, N-tertbutylacrylamide,butoxymethylacrylamide, N,N-dimethylacrylamide, sodium acrylamidomethylpropane sulfonic acid, vinyl alcohol, vinyl acetate, N-vinylpyrrolidone, maleic acid, and combinations thereof.

As used herein, the monomers described above may be in either their saltor acid forms.

Preferably, the binder is of a structure wherein p=2; R¹, R⁴, R⁵, and R⁶are hydrogen in formula IV of step A; and the mer units of step B areacrylic acid and acrylamide.

Additionally, the binder may be of a structure wherein p=3; R⁵, R⁶, andR¹ are hydrogen; R⁴ is methyl in formula IV of step A; and the mer unitsof step B are acrylic acid and acrylamide.

Moreover, for the practice of this invention, mer units of generalstructure IV with polyoxy N-pendant groups may also be effective, aswell as the alkyloxy groups described above. For example multihydroxyN-pendant groups such as those alkyl derivatives having dihydroxy andtrihydroxy, as well as alkyl derivatives containing diether and triethermoieties may also be effective.

The invention is also an unfired, ceramic precursor material comprisinga mixture of:

A) a ceramic powder selected from the group consisting of aluminumoxide, silicon nitride, aluminum nitride, silicon carbide, siliconoxide, magnesium oxide, lead oxide, zirconium oxide, titanium oxide,steatite, barium titanate, lead zirconate titanate, clays, ferrite,yttrium oxide, zinc oxide, tungsten carbide, sialon, neodymium oxide andcombinations thereof and

B) a water-soluble polymer having:

i) a mer unit of the formula ##STR13## wherein R¹ is selected from thegroup consisting of hydrogen, and C₁ -C₃ alkyl; p is an integer from1-10; R⁴ is selected from the group consisting of hydrogen, phosphate,sulfate and C₁ -C₂₀ alkyl; R⁵ and R⁶ are selected from the groupconsisting of hydrogen, carboxylate, C₁ -C₃ alkyl, and a cycloalkylgroup of 1 to 6 carbon atoms formed by the linkage of R⁵ and R⁶ as aring; and

ii) a mer unit selected from the group consisting of acrylic acid,methacrylic acid, acrylamide, maleic anhydride, itaconic acid, vinylsulfonic acid, styrene sulfonate, N-tertbutylacrylamide,butoxymethylacrylamide, N,N-dimethylacrylamide, sodium acrylamidomethylpropane sulfonic acid, vinyl alcohol, vinyl acetate, N-vinylpyrrolidone, maleic acid, and combinations thereof.

Preferably, the water-soluble polymer of the method described above hasa structure wherein p=2; R¹, R⁴, R⁵, and R⁶ are hydrogen for formula IVof step i; and the mer units of step ii are acrylic acid and acrylamide.

Alternatively, the water-soluble polymer of the method described abovehas a structure wherein p=3; R⁵, R⁶, and R¹ are hydrogen; R⁴ is methylfor formula IV of step i and the mer units of step ii are acrylic acidand acrylamide.

The invention is also a method for preparing a ceramic material, whichcomprises the steps of:

A) mixing a ceramic powder with an aqueous solution containing awater-soluble polymer to produce a slurry, said water-soluble polymerhaving:

i) a mer unit of the formula ##STR14## wherein R¹ is selected from thegroup consisting of hydrogen, and C₁ -C₃ alkyl; p is an integer from1-10; R⁴ is selected from the group consisting of hydrogen, phosphate,sulfate and C₁ -C₂₀ alkyl; R⁵ and R⁶ are selected from the groupconsisting of hydrogen, carboxylate, C₁ -C₃ alkyl, and a cycloalkylgroup of 1 to 6 carbon atoms formed by the linkage of R⁵ and R⁶ as aring; and

ii) a mer unit selected from the group consisting of acrylic acid,methacrylic acid, acrylamide, maleic anhydride, itaconic acid, vinylsulfonic acid, styrene sulfonate, N-tertbutylacrylamide,butoxymethylacrylamide, N,N-dimethylacrylamide, sodium acrylamidomethylpropane sulfonic acid, vinyl alcohol, vinyl acetate, N-vinylpyrrolidone, maleic acid, and combinations thereof;

B) drying the slurry by a process selected from the group consisting offluidized bed spray drying, and spray drying to produce particles whichinclude said copolymer;

C) compacting the particles by a process selected from the groupconsisting of dry pressing, roll compaction and isostatic pressing toproduce an aggregate structure; and

D) heating the aggregate structure to produce a fired ceramic material.

Preferably, the water-soluble polymer of the method described above hasa structure wherein p=2; R¹, R⁴, R⁵, and R⁶ are hydrogen for formula IVof step I and the mer units of step ii are acrylic acid and acrylamide.

Alternatively, the water-soluble polymer of the method described abovehas a structure wherein p=3; R⁵, R⁶, and R¹ are hydrogen; R⁴ is methylfor formula IV of step i and the mer units of step ii are acrylic acidand acrylamide.

Furthermore, in the method described above, the particles may beproduced by granulation and the step of compacting the particles toproduce an aggregate structure may be selected from the group consistingof dry pressing and isostatic pressing.

Alternatively, other methods of making ceramics which are suitable forthe purposes of this invention include extrusion, jiggering, tapecasting and slip casting.

The invention is also a method for dispersing one or more ceramicmaterials in an aqueous medium, comprising utilizing an effectivedispersing amount of a polymeric dispersant comprising a water-solublepolymer having:

A) a mer unit of the formula ##STR15## wherein R¹ is selected from thegroup consisting of hydrogen, and C₁ -C₃ alkyl; p is an integer from1-10; R⁴ is selected from the group consisting of hydrogen, phosphate,sulfate and C₁ -C₂₀ alkyl; R⁵ and R⁶ are selected from the groupconsisting of hydrogen, carboxylate, C₁ -C₃ alkyl, and a cycloalkylgroup of 1 to 6 carbon atoms formed by the linkage of R⁵ and R⁶ as aring; and

B) a mer unit selected from the group consisting of acrylic acid,methacrylic acid, acrylamide, maleic anhydride, itaconic acid, vinylsulfonic acid, styrene sulfonate, N-tertbutylacrylamide,butoxymethylacrylamide, N,N-dimethylacrylamide, sodium acrylamidomethylpropane sulfonic acid, vinyl alcohol, vinyl acetate, N-vinylpyrrolidone, maleic acid, and combinations thereof.

Preferably, the water-soluble polymer of the method described above hasa structure wherein p=2; R¹, R⁴, R⁵, and R⁶ are hydrogen for formula IVof step A; and the mer units of step B are acrylic acid and acrylamide.

Alternatively, the water-soluble polymer of the method described abovehas a structure wherein p=3; R⁵, R⁶, and R¹ are hydrogen; R⁴ is methylfor formula IV of step A; and the mer units of step B are acrylic acidand acrylamide.

For the practice of this invention, the one or more ceramic materialsmay be selected from the group consisting of alumina, aluminum nitride,aluminum titanate, lead titanate, boron nitride, silicon, siliconcarbide, sialon, zirconium nitride, zirconium carbide, zirconium boride,boron carbide, tungsten carbide, tungsten boride, tin oxide, rutheniumoxide, yttrium oxide, magnesium oxide, calcium oxide, and ferrites.

Moreover, the method may include an aqueous dispersion of ceramicmaterial.

The following examples are presented to describe preferred embodimentsand utilities of the invention and are not meant to limit the inventionunless otherwise stated in the claims appended hereto.

EXAMPLE 1

The synthesis of an ammonium acrylate/N-(hydroxyethoxy)ethyl acrylamidecopolymer was effected with the following reactants in the followingamounts:

    ______________________________________                                        Reactant             Amount (g)                                               ______________________________________                                        Poly(AA), 25.6 weight % in water                                                                   100.00                                                     Aminoethoxyethanol 11.92                                                      Ammonium Hydroxide, 29 weight % 2.51                                        ______________________________________                                    

To prepare the polymer, poly(AA) (25.6 weight percent poly(acrylic acid)solution, pH=3.8, 16,000 MW) was placed in a beaker, which was cooledusing an ice bath. Aminoethoxyethanol (available from HuntsmanPetrochemical Co., in Houston, Tex.) was added dropwise into thepoly(acrylic acid)/water solution with vigorous stirring. Afterwards,the solution was stirred for another 15 minutes. The pH of the reactionmixture was measured using water-wet pH strips. Aqueous caustic wasadded to adjust the pH to about 5. Next, the reaction mixture wastransferred into a 300 mL Parr reactor with a pressure rating of atleast 800 psi. The reactor then was assembled and purged with nitrogenfor 60 minutes. The Parr reactor was then slowly heated to 160° C. (orless, as the case may be) and held at that temperature for 8 hours (ormore, as the case may be). Afterwards, the reactor was cooled to roomtemperature and the pressure released. The product was then transferredto storage.

¹³ C NMR confirmed product formation. The content ofN-(hydroxyethoxy)ethyl acrylamide was 21 mole %, based on the totalmoles of mer units on the polymer, which represents both secondary amideand imide mer units. The polymer's molecular weight was 24,000.

EXAMPLE 2

The synthesis of an ammonium acrylate/acrylamide/N-(hydroxyethoxy)ethylacrylamide terpolymer was effected in the following manner with thereactants in the amounts listed below:

    ______________________________________                                        Reactant             Amount (g)                                               ______________________________________                                        Poly(NH.sub.4 AA/AcAm), 50/50 mol %                                                                300.00                                                     solution polymer, 38.2 weight %                                               Aminoethoxyethanol 114.00                                                   ______________________________________                                    

To prepare the polymer, Poly(NH₄ AA/AcAm) (50/50 mol % ammoniumacrylate/acrylamide copolymer, 38.2 weight percent, pH=5.5, 33,000 MW)was placed in a beaker, which was cooled using an ice bath.Aminoethoxyethanol (available from Huntsman Petrochemical Co., inHouston, Tex.) was added dropwise into the above water solution withvigorous stirring (pH=10. 1). Afterwards, the solution was stirred foranother 15 minutes. The pH of the reaction mixture was measured usingwater-wet pH strips. Next, the reaction mixture was transferred into a600 mL Parr reactor with a pressure rating of at least 800 psi. Thereactor then was assembled and purged with nitrogen for 60 minutes. TheParr reactor was then slowly heated to 138° C. and held at thattemperature for 14 hours. Afterwards, the reactor was cooled to roomtemperature and the pressure released. The product was then transferredto storage.

¹³ C NMR confirmed product formation. The content ofN-(hydroxyethoxy)ethyl acrylamide was 33.3 mole %, based on the totalmoles of mer units on the polymer. The polymer had a molecular weight of35,000, and a mole ratio of N-(hydroxyethoxy)ethyl acrylamide/acrylicacid/acrylamide of 33/41/26.

EXAMPLE 3

The synthesis of a sodium acrylate/acrylamide/N-(hydroxyethoxy)ethylacrylamide terpolymer was effected in the following manner with thereactants in the amounts listed below:

    ______________________________________                                        Reactant            Amount (g)                                                ______________________________________                                        Poly(NaAA/AcAm), 50/50 mol %                                                                      100.00                                                      solution polymer, 32.0 weight %                                               Aminoethoxyethanol 32.00                                                      Sulfuric Acid (95%) 11.5                                                    ______________________________________                                    

To prepare the polymer, Poly(NaAA/AcAm) (50/50 mol % sodiumacrylate/acrylamide copolymer, 32.0 weight %, pH=5.2, 11,000 MW) wasplaced in a beaker, which was cooled using an ice bath.Aminoethoxyethanol (available from Huntsman Petrochemical Co., inHouston, Tex.) was added dropwise into the above water solution withvigorous stirring. Afterwards, the solution was stirred for another 15minutes. The pH of the reaction mixture was measured using water-wet pHstrips. Sulfiric acid was added to adjust the pH to about 5.6. Next, thereaction mixture was transferred into a 300 mL Parr reactor with apressure rating of at least 800 psi. The reactor then was assembled andpurged with nitrogen for 60 minutes. The Parr reactor was then slowlyheated to 138° C. and held at that temperature for 12 hours. Afterwards,the reactor was cooled to room temperature and the pressure released.The product was then transferred to storage.

¹³ C NMR confirmed product formation. The content ofN-(hydroxyethoxy)ethyl acrylamide was 33 mole %, based on the totalmoles of mer units on the polymer. The mole ratio was 42/22/33 ofacrylic acid/acrylamide(including 3% imide merunits)/N-(hydroxyethoxy)ethyl acrylamide (including imide mer units).The product polymer had a molecular weight of 12,000.

EXAMPLE 4

The synthesis of a sodium acrylate/acrylamide/N-Methoxypropyl acrylamideterpolymer was effected in the following manner with the reactants inthe amounts listed below:

    ______________________________________                                        Reactant            Amount(g)                                                 ______________________________________                                        Poly(NaAA/AcAm), 50/50 mol %                                                                      100.00                                                      solution polymer, 32.0 weight %                                               Methoxypropylamine 23.32                                                      Sulfuric Acid (95%) 11.23                                                   ______________________________________                                    

To prepare the polymer, Poly(NaAA/AcAm) (50/50 mol %, 32.0 weight %,pH=5.2, 11,000 MW) was placed in a beaker, which was cooled using an icebath. Methoxypropylamine (available from Aldrich Chem. Co., inMilwaukee, Wis.) was added dropwise into the above water solution withvigorous stirring. Afterwards, the solution was stirred for another 15minutes. The pH of the reaction mixture was measured using water-wet pHstrips. Sulfuric acid was added to adjust the pH to about 5.6. Next, thereaction mixture was transferred into a 300 mL Parr reactor with apressure rating of at least 800 psi. The reactor then was assembled andpurged with nitrogen for 60 minutes. The Parr reactor was then slowlyheated to 138° C. and held at that temperature for 12 hours. Afterwards,the reactor was cooled to room temperature and the pressure released.The product was then transferred to storage.

¹³ C NMR confirmed product formation. The content of methoxypropylacrylamide was 34.2 mole %, based on the total moles of mer units on thepolymer. The mole ratio of the product was 41/17/34 which representsacrylic acid/acrylamide (including 6% imide mer units)/methoxypropylacrylamide (including imide mer units). The product's molecular weightwas 11,000.

EXAMPLE 5

The synthesis of a sodium acrylate/acrylamide/N-hydroxy(ethylamino)ethylacrylamide terpolymer was effected in the following manner with thereactants in the amounts listed below:

    ______________________________________                                        Reactant            Amount(g)                                                 ______________________________________                                        Poly(NaAA/AcAm), 50/50 mol %                                                                      80.00                                                       solution polymer, 24.0 weight %                                               (Aminoethylamine)ethanol 19.02                                                Sulfuric Acid (95%) 12.23                                                   ______________________________________                                    

To prepare the polymer, Poly(NaAA/AcAm) (50/50 mol %, 24.0 weight %,pH=3.5, 15,000 MW) was placed in a beaker, which was cooled using an icebath. (Aminoethylamino)ethanol (available from Aldrich Chem. Co., inMilwaukee, Wis.) was added dropwise into the above water solution withvigorous stirring. Afterwards, the solution was stirred for another 15minutes. The pH of the reaction mixture was measured using water-wet pHstrips. Sulfuric acid was added to adjust the pH to about 5.6. Next, thereaction mixture was transferred into a 300 mL Parr reactor with apressure rating of at least 800 psi. The reactor then was assembled andpurged with nitrogen for 60 minutes. The Parr reactor was then slowlyheated to 138° C. and held at that temperature for 14 hours. Afterwards,the reactor was cooled to room temperature and the pressure released.The product was then transferred to storage.

¹³ C NMR confirmed product formation. The content of hydroxy(ethylamino)ethyl acrylamide was 46 mole %, based on the total moles of mer units onthe polymer, representing both secondary amide and imide mer units. Thepolymer also contained 51% of acrylic acid units. The product polymer'smolecular weight was 15,000.

EXAMPLE 6

The synthesis of an acrylic acid/acrylamide/N-(hydroxyethoxy)ethylacrylamide terpolymer was effected in the following manner with thereactants in the amounts listed below:

    ______________________________________                                        Reactant          Amount(g)                                                   ______________________________________                                        Poly(AcAm), 50 weight %                                                                         50.00                                                         Aminoethoxyethanol 12.9                                                       Deionized water 50.0                                                          Sulfuric Acid (95%) 6.1                                                     ______________________________________                                    

To prepare the polymer, Poly(AcAm) (50 wt %, available from AldrichChemical Co., 10,000 MW) was placed in a beaker, which was cooled usingan ice bath. Aminoethoxyethanol (available from Huntsman PetrochemicalCo., in Houston, Tex.) was added dropwise into the above water solutionwith vigorous stirring. Afterwards, the solution was stirred for another15 minutes. The pH of the reaction mixture was measured using water-wetpH strips. Sulfuric acid was added to adjust the pH to about 5.6. Next,the reaction mixture was transferred into a 300 mL Parr reactor with apressure rating of at least 800 psi. The reactor then was assembled andpurged with nitrogen for 60 minutes. The Parr reactor was then slowlyheated to 138° C. and held at that temperature for 14 hr. Afterwards,the reactor was cooled to room temperature and the pressure released.The product was then transferred to storage.

³ C NMR confirmed product formation. The content of N-(hydroxyethoxy)ethyl acrylamide was 19.6 mole %, based on the total moles of mer unitson the polymer. The product's mole ratio was 32/44/20 which representsacrylic acid/acrylamide/N-(hydroxyethoxy)ethyl acrylamide.

EXAMPLE 7

The synthesis of a 33/50/17 mole percent acrylicacid/acrylamide/N-(hydroxyethyl) acrylamide terpolymer was effected inthe following manner. To 100 g of a 52/48 mole ratio AA/AcAm copolymer(42.7% polymer actives, weight average molecular weight=34,100) in aParr reactor was added 17.4 g of ethanolamine. The pH was adjusted with8.32 g of 36% hydrochloric acid to between 5.0 to 5.5. The solution waspurged with nitrogen for 1.0 hour and heated at 138-142° C. for about 8hours. NMR analysis results indicated the terpolymer composition was38/52/10 N-(hydroxyethyl) acrylamide/AA/AcAm. The weight averagemolecular weight of the product was 128,000, indicating the polymer waslightly crosslinked. To the stirred half amount of the product was addeddropwise 50% NaOH solution (19.24 g) at pH<11.39. The solution wasfurther stirred for 3.5 hours at room temperature. The pH was adjustedto about 7 with 36% hydrochloric acid. The weight average molecularweight was 42,600. NMR analysis results showed this product was aterpolymer of 33/50/17 N-(hydroxyethyl)acrylamide/AA/Am.

EXAMPLE 8

The synthesis of a 35/51/14 mole percent N-(hydroxyethyl)acrylamide/acrylic acid/acrylamide terpolymer was effected in thefollowing manner. To 100 g of a 52/48 AA/Am copolymer (42.7% polymeractives, weight average molecular weight 34,100) in a Parr reactor wasadded 25.3 g. of ethanolamine. The pH was adjusted with 18.8 g of 36%hydrochloric acid to about 5.3. The solution was purged with nitrogenfor 1.0 hour and heated at 136-138° C. for about 7 hours. 37.0 g of 50%NaOH was added dropwise to the stirred solution at pH<12 and at roomtemperature. After the solution was stirred for further 5 hours, the pHwas adjusted with 36% hydrochloric acid to 8.5. NMR analysis resultsindicated the terpolymer composition was 35/51/14 N-(hydroxyethyl)acrylamide/AA/Am. The weight average molecular weight of the terpolymerwas 31,000.

EXAMPLE 9

To determine the dispersancy of the polymers, the following experimentalprocedure was followed. 1500 g slips were prepared to 80 weight percentalumina powder (99.5% calcinated alpha alumina oxide available fromAlcan, C90 LSB Alumina) in water using 0.25 weight percent(polymer/powder) of the polymer to be tested.

Each slip was milled 3 hours in a 1-liter jar mill using 1500 g millingmedia. Then, resulting slips were filtered through a 60 mesh screen, andBrookfield viscosity was measured using an LVT type viscometer using a#2 spindle. For comparison purposes, a commercially available, commonalumina additive polymer was utilized. Polymer B is an ammoniumpoly(methacrylate) available from R.T. Vanderbilt Co., Norwalk, Conn.Polymer A is a polymer synthesized according to the procedure of Example2.

The viscosity of a slurry must be suitable for necessary handling andspray drying. Although spray dry equipment and running conditions may beadjusted to handle a variety of viscosities, larger particles willresult from higher viscosity slurries. The resultant large particles maylead to larger interstices between particles and hence a lower strength.The binder may contribute to viscosity of the continuous phase of theslurry by virtue of its molecular weight, solubility, conformation insolution, and possible incompatibility with the combination of powderand dispersant. Since a lower viscosity is more desirable for ceramicapplications, the results of Table I show that a polymer of thisinvention, prepared in accordance with the procedure of Example 2, worksbetter than the common treatment.

                  TABLE I                                                         ______________________________________                                        Dispersancy in Alumina                                                                  Brookfield Viscosity (cP)                                           Polymer   6 rpm  12 rpm      30 rpm                                                                              60 rpm                                     ______________________________________                                        A         100    88          70    65                                           B 300 225 160 105                                                           ______________________________________                                    

EXAMPLE 10

The polymers were also tested in order to determine the effects of slipviscosity as a function of binder type, according to the followingprocedure. Deflocculated slips were prepared as in the procedure ofExample 9. To each slip so prepared, the polymeric treatment to betested was added, to be a total of 4.0 weight percent (polymer/powder)level. Next, each binder-containing slip was propeller mixed at 800 rpmfor one hour. For any necessary dilution, deionized water was added toattain the tabulated powder solids level. Finally, the slip viscositywas measured using the method described in Example 9.

The results of Table II illustrate that even though the bindercomposition was varied, the polymers of this invention caused lowerviscosity of the slip than the current commercially available polymertreatment. In Table II, Polymer C is a poly(vinyl alcohol) which has amolecular weight of 30,000 to 50,000 and is 88% hydrolyzed. It isavailable from Air Products of Allentown, Pa. Polymer A is a polymersynthesized according to the procedure in Example 2. For each polymertested, 4 weight percent was utilized, and the viscosity was measured at3.14 sec⁻¹.

                  TABLE II                                                        ______________________________________                                        Slip Viscosity as a Function of Binder Type                                       Slip Powder Solids                                                                         Polymer C      Polymer A                                       Weight Percent Slip BFV.sup.1 (cP) Slip BFV.sup.1 (cP)                      ______________________________________                                        76.4         >10,000        440                                                 74.8 8,200 170                                                                72 840  20                                                                    70 360 --                                                                   ______________________________________                                         .sup.1 Brookfield viscosity                                              

EXAMPLE 11

A copolymer synthesized by the procedure described in Example 2 above,was tested as a binder for alumina particles of the type that arecommonly used for producing ceramic materials.

The slip preparation described in Example 10 was utilized in thisExample to further examine the characteristics of the binders.

The milled slurry was spray dried in a Yamato DL41 laboratory spraydryer. Dryer operating conditions were: 250° C. air inlet temperature,atomizing air setting of 1.2, slurry feed pump setting of 5, and dryingair feed rate of 0.7 cubic meters per minute. A dry powder was producedwhich was recovered, screened and stored overnight in a 20 percentrelative humidity chamber.

The screened powder was pressed into nine pellets in a Carver laboratorypress, three at 5,000 pounds per square inch pressing force, three at15,000 pounds per square inch pressing force, and three at 25,000 poundsper square inch pressing force. The pellets were approximately 28.7millimeters in diameter and 5 to 6 millimeters in height. The dimensionsand weights of the pellets were measured and the pellets were crushed todetermine the force required to break them. Diametral compressionstrength (DCS) for each of the pellets was determined from the breakingforce and the pellet dimensions. The average diametral compressionstrength in megapascals for each set of three pellets is presented belowin Table III.

Green body diametral compressional strength is important in ceramicsapplications for the following reasons. The principal function of thebinder is to hold the compacted form together after pressing. The methodutilized for determination of suitable "green strength" is the diametralcompression strength or DCS of a cylindrical section across itsdiameter. DCS is actually a measure of tensile strength. The unit ofmeasurement of pressure tolerance is the megapascal (Mpa). Typicalvalues for DCS of "green" parts are in the range of 0.3-3.0 Mpa. PolymerA is a polymer prepared according to the procedure in Example 2. PolymerC is the conventional additive described in Example 10. Therefore, sincea higher DCS value indicates a more efficient binder, Table III showsthat the polymers of the instant invention are more efficient than aconventional treatment. D is another additive that is often used inconjunction with these polymeric treatments for ceramic applications.

Since a greater density is more desirable, the results of Table IIIillustrate that the polymers of the instant invention are moreadvantageous in this respect also, as indicated by the higher numbersobtained than in the case of the conventional treatment.

The springback characteristic is another important measure of theefficiency of a polymer for ceramics applications for the followingreasons. Upon filling a die, the resulting compacted part must besmoothly ejected, be as dense as possible, and not suffer significantdimensional change from that of the die. Chemical additives have a majoreffect on the desired lubricity. The compressed powder will undergostress relaxation in the form of expansion on release from the die. Thisphenomenon is referred to as "springback" and is undesirable from thestandpoint of dimensional accuracy as well as density and strength. Forthis example, D was used as a plasticizer. Maintenance of net shape isimportant, as the occurrence of a larger amount of springback can causelamination defects, or undesirable density gradients. Therefore, thelower values for springback obtained for the polymers of this inventionin Table III demonstrate that such polymers are more efficient than theconventional treatment.

The pressure required for die ejection was also measured. The same testequipment was utilized as described above, except that after the pelletis pressed, a plunger on the bottom of the apparatus is utilized toapply force to the die. A lower pressure is more desirable, and wasobtained by the use of polymers of the instant invention over polymersconventionally utilized for ceramic purposes.

                  TABLE III                                                       ______________________________________                                        Comparison of Green Body Properties                                                     Polymeric Treatment                                                 Pressure (PS)                                                                           A      C      A + D.sup.1                                                                         C + D.sup.1                                                                         A + D.sup.2                                                                         C + D.sup.2                         ______________________________________                                                Green Body Diametrial Compressional Strength (MPa)                     5,000    0.64   0.20   0.55  0.45  0.45  0.38                                  15,000 1.76 0.98 1.24 1.01 1.04 0.79                                          25,000 2.42 1.19 1.79 1.30 1.31 0.91                                                Pellet Green Density (g/cc)                                            5,000    2.28   2.09   2.30  2.23  2.33  2.34                                  15,000 2.52 2.38 2.51 2.43 2.54 2.50                                          25,000 2.60 2.43 2.61 2.51 2.60 2.57                                                Percent Springback in Green Bodies                                     5,000    0.06   0.22   -0.02 0.19  0.11  0.12                                  15,000 0.11 0.22 0.12 0.19 0.14 0.18                                          25,000 0.16 0.23 0.14 0.19 0.15 0.18                                                Pressure Required for Die Ejection (PSI)                               5,000    0.00   7.93   0.96  29.16 7.46  22.47                                 15,000 19.86 49.37 26.57 73.94 39.08 64.57                                    25,000 41.30 77.87 42.12 101.14 59.48 92.00                                 ______________________________________                                         D.sup.1 = poly(ethylene oxide/propylene oxide) ether linked to                (1,2ethandiyldintrilo) tetrakis [propanol], 0.8 weight percent                D.sup.2 = as D.sup.1 above, 3.0 weight percent                           

EXAMPLE 12

The procedures utilized in Example 11 were utilized to obtain theresults of Table IV. Rather than utilize a range of pressures as in theprevious example, the characteristics were evaluated at a singledensity. The pressure which was required to produce that density wasrecorded in the table. The polymers A, C and D are as defined in Example11 above. Even when measured at pellets pressed to a constant density,the polymers of the instant invention provide superior performance overthe conventional polymeric treatment.

                                      TABLE IV                                    __________________________________________________________________________    Comparative Green Body Properties at Green Density 2.4 g/mL                   Polymeric                                                                            Press Pressure         Ejection Force                                    Treatment Required (PSI) DCS (MPa) % Springback (psi)                       __________________________________________________________________________    A      10,000  1.22   0.08    10                                                C 19,200 1.1 0.23 63                                                          A + D.sup.1  9,700 0.94 0.04 13                                               C + D.sup.1 13,300 0.88 0.19 67                                               A + D.sup.2  8,200 0.65 0.12 18                                               A + D.sup.2  8,800 0.56 0.14 39                                             __________________________________________________________________________     D.sup.1 = poly(ethylene oxide/propylene oxide) ether linked to                (1,2ethandiyldintrilo) tetrakis [propanol], 0.8 weight percent                D.sup.2 = as D.sup.1 above, 3.0 weight percent                           

Changes can be made in the composition, operation and arrangement of themethod of the present invention described herein without departing fromthe concept and scope of the invention as defined in the followingclaims:

We claim:
 1. An unfired, ceramic precursor material comprising a mixtureof:A) a ceramic powder selected from the group consisting of aluminumoxide, silicon nitride, aluminum nitride, silicon carbide, siliconoxide, magnesium oxide, lead oxide, zirconium oxide, titanium oxide,steatite, barium titanate, lead zirconate titanate, clays, ferrite,yttrium oxide, zinc oxide, tungsten carbide, sialon, neodymium oxide andcombinations thereof and B) a water-soluble polymer having:i) a mer unitof the formula ##STR16## wherein R¹ is selected from the groupconsisting of hydrogen, and C₁ -C₃ alkyl; p is an integer from 1-10; R⁴is selected from the group consisting of hydrogen, phosphate, sulfateand C₁ -C₂₀ alkyl; R⁵ and R⁶ are selected from the group consisting ofhydrogen, carboxylate, C₁ -C₃ alkyl, and a cycloalkyl group of 1 to 6carbon atoms formed by the linkage of R⁵ and R⁶ as a ring; and ii) oneor more mer units selected from the group consisting of acrylic acid,methacrylic acid, acrylamide, maleic anhydride, itaconic acid, vinylsulfonic acid, styrene sulfonate, N-tertbutylacrylamide,butoxymethylacrylamide, N,N-dimethylacrylamide, sodium acrylamidomethylpropane sulfonic acid, vinyl alcohol, vinyl acetate, N-vinyl pyrrolidoneand maleic acid.
 2. The unfired, ceramic precursor material of claim 1wherein p=2; R¹, R⁴, R⁵, and R⁶ are hydrogen for formula IV of step i;and the mer units of step ii are acrylic acid and acrylamide.
 3. Theunfired, ceramic precursor material of claim 1 wherein p=3; R⁵, R⁶, andR¹ are hydrogen; R⁴ is methyl for formula IV of step i and the mer unitsof step ii are acrylic acid and acrylamide.
 4. A method for preparing aceramic material, which comprises the steps of:A) mixing a ceramicpowder with an aqueous solution containing a water-soluble polymer toproduce a slurry, said water-soluble polymer having:i) a mer unit of theformula ##STR17## wherein R¹ is selected from the group consisting ofhydrogen, and C₁ -C₃ alkyl; p is an integer from 1-10; R⁴ is selectedfrom the group consisting of hydrogen, phosphate, sulfate and C₁ -C₂₀alkyl; R⁵ and R⁶ are selected from the group consisting of hydrogen,carboxylate, C₁ -C₃ alkyl, and a cycloalkyl group of 1 to 6 carbon atomsformed by the linkage of R⁵ and R⁶ as a ring; and ii) one or more merunits selected from the group consisting of acrylic acid, methacrylicacid, acrylamide, maleic anhydride, itaconic acid, vinyl sulfonic acid,styrene sulfonate, N-tertbutylacrylamide, butoxymethylacrylamide,N,N-dimethylacrylamide, sodium acrylamidomethyl propane sulfonic acid,vinyl alcohol, vinyl acetate, N-vinyl pyrrolidone and maleic acid; B)drying the slurry by a process selected from the group consisting offluidized bed spray drying and spray drying to produce particles whichinclude said copolymer; C) compacting the particles by a processselected from the group consisting of dry pressing, roll compaction,isostatic pressing to produce an aggregate structure; and D) heating theaggregate structure to produce a fired ceramic material.
 5. The methodof claim 4 wherein p=2; R¹, R⁴, R⁵, and R⁶ are hydrogen for formula IVof step i and the mer units of step ii are acrylic acid and acrylamide.6. The method of claim 4 wherein p=3; R⁵, R⁶, and R¹ are hydrogen; R⁴ ismethyl for formula IV of step i and the mer units of step ii are acrylicacid and acrylamide.
 7. The method of claim 4 wherein the particles areproduced by granulation and the step of compacting the particles toproduce an aggregate structure is selected from the group consisting ofdry pressing and isostatic pressing.
 8. A method for dispersing one ormore ceramic materials in an aqueous medium, comprising utilizing aneffective dispersing amount of a polymeric dispersant comprising awater-soluble polymer having:A) a mer unit of the formula ##STR18##wherein R¹ is selected from the group consisting of hydrogen, and C₁ -C₃alkyl; p is an integer from 1-10; R⁴ is selected from the groupconsisting of hydrogen, phosphate, sulfate and C₁ -C₂₀ alkyl; R⁵ and R⁶are selected from the group consisting of hydrogen, carboxylate, C₁ -C₃alkyl, and a cycloalkyl group of 1 to 6 carbon atoms formed by thelinkage of R⁵ and R⁶ as a ring; and B) a mer unit selected from thegroup consisting of acrylic acid, methacrylic acid, acrylamide, maleicanhydride, itaconic acid, vinyl sulfonic acid, styrene sulfonate,N-tertbutylacrylamide, butoxymethylacrylanide, N,N-dimethylacrylamide,sodium acrylamidomethyl propane sulfonic acid, vinyl alcohol, vinylacetate, N-vinyl pyrrolidone, maleic acid, and combinations thereof. 9.The method of claim 8 wherein p=2; R¹, R⁴, R⁵, and R⁶ are hydrogen forformula IV of step A; and the mer units of step B are acrylic acid andacrylamide.
 10. The method of claim 8 wherein p=3; R⁵, R⁶, and R¹ arehydrogen; R⁴ is methyl for formula IV of step A; and the mer units ofstep B are acrylic acid and acrylamide.
 11. The method of claim 8wherein the one or more ceramic materials is selected from the groupconsisting of alumina, aluminum nitride, aluminum titanate, leadtitanate, boron nitride, silicon, silicon carbide, sialon, zirconiumnitride, zirconium carbide, zirconium boride, boron carbide, tungstencarbide, tungsten boride, tin oxide, ruthenium oxide, yttrium oxide,magnesium oxide, calcium oxide, and ferrites.
 12. An aqueous dispersionof ceramic material prepared according to the method of claim 8.